Linkage apparatus having a mechanism for dampening vibrations

ABSTRACT

Linkage apparatus for connecting a use device, preferably a vibrating cable plow, to a ground-engaging vehicle. The linkage apparatus comprises a first arm member having a first mechanism for connecting the first end to the vehicle, a second arm member having a second mechanism for connecting the second end to the use device, a third mechanism for pivotally connecting the first and second arm members, and a mechanism for dampening vibrations between the first and second arm members perferably including resilient members such as air cushion bags.

FIELD OF THE INVENTION

The present invention relates to a linkage apparatus for connecting ause device, most preferably a vibrating cable plow apparatus, to aground-engaging vehicle, wherein the linkage apparatus includes amechanism for dampening vibrations.

BACKGROUND OF THE INVENTION

Cable plows of the type disclosed herein have been utilized for manyyears to lay many types of cables, flexible pipes, conduits, etc. Thecable or pipe has been passed into a trench, dug by a plow-blade,through a chute, or some other mechanism for guiding the cable or pipe,which trails the leading edge of the plow-blade. In either case, thecable generally passes into an opening in the ground created by theblade from a spool mounted on the vehicle which pulls the plowapparatus. Because the plow must be pulled through very rough and, attimes, heavily packed terrain, the ground-engaging vehicle which pullsthe plow apparatus has had to be a very large and powerful tractor.

Vehicles pulling cable plows have generally been required to travel atrelatively slow speeds, laying cable at a rate in a range of inches perminute. In this regard, it has been found that vibration, orreciprocating movement of the plow-blade, is effective to work the soiland reduce the tractive pulling force required to pull the blade throughthe ground. Where such vibration or reciprocating movement of the bladewas employed, it was found that smaller tractors possessing lesstractive pulling power could be used to lay cable. This ability to usesmaller tractors offered several advantages including less grounddisturbance, more maneuverability, faster cable laying, greatermobility, etc.

Following the development of vibratory cabling laying plows, however, itbecame apparent that the vibrations from the plow had a negative effecton the operators of such machinery, and upon the working parts of thevehicle pulling the plow. It proved to be very stressful for operatorsto be subjected to constant vibrations for long periods of time eachday. In addition, the parts of the vehicle tended to come apart and needrepeated tightening. The vehicles also seem to wear faster.

Therefore, efforts were made to dampen the vibrations emanating from theplow apparatus. For example, U.S. Pat. No. 3,618,237 discloses a framesupport for a cable laying plow apparatus having torque cushioningelements which absorb some of the reciprocable motion of the support inan attempt to isolate the frame from the supporting structure. Afour-point support apparatus is also provided to cooperate to define aparallelogram-type linkage apparatus.

U.S. Pat. No. 3,561,539 discloses a vibratory cable plow having asharpened plow point at an unspecified angle and a plurality ofresilient pads designed to enhance vibratory movement and dampen thetransfer of vibratory movement from the enlongated plowblade to themounting frame. Unfortunately, none of these dampening means adequatelydampens vibrations from the vibration or reciprocating device.

The vibratory plow apparatus of U.S. Pat. No. 3,561,539 also discloses aparallelogram-type apparatus for raising and lowering the plow whilemaintaining the plow-blade in a substantially vertical orientation. U.S.Pat. No. 3,684,030 also discloses a parallelogram-type support structurefor a plow-blade including a number of digger teeth which projectforwardly and downwardly from the plow-blade. Motive mechanisms are alsodisclosed for swinging the linkage mechanism on a vertical axis withrespect to the vehicle, and for lifting the lower arm of the linkagemechanism and hence the plow-blade.

One of the advantages of the parallelogram-type linkage mechanism isthat the plow may be raised without changing the vertical orientation ofthe plow to the soil. As compared to three point linkage mechanisms,this enables the cable plow to continue laying cable at the lowestpossible depth when the plow must be raised to traverse over immovableobjects such as pipes or large rocks which may be buried in the soil.When a three point lift mechanism is employed, the plow is generallyraised such that the plow is angled backwards and away from the vehicle.The backside of the plow-blade where the cable guide outlet mechanism isgenerally located, is thereby raised to a greater degree than theleading edge of the plow-blade which must traverse across the buriedobject. Since the backside of the plow-blade angles upward from theleading edge of the plow-blade, the cable can come out of the guidemechanism as much as a foot higher than the leading edge of theplow-blade. The parallelogram-type linkage mechanism allows the plow tobe raised vertically without creating this angle, thereby allowing thecable to be laid at the greatest depth possible when traversing overimmovable buried objects.

One disadvantage of the parallelogram-type linkage mechanism is thatalthough it enables one to lay cable at the lowest depth possible whentraversing over immovable buried objects, it is not possible to maintainthe blade at a desired orientation to the ground when traveling throughirregular terrain. In irregular terrain, when the vehicle and theplow-blade may simultaneously engage ground at different pitches orslopes, the angle of the plow-blade will depend on the slope of theground to which the vehicle is engaged. This slope may be entirelydifferent from the slope of the ground in which the plow-blade isengaged. In such a situation, the plow-blade will not be perpendicularto the ground. This can result in the backside of the plow-blade beingat a different depth than the leading edge of the plow-blade. If thebackside is higher than the leading edge, the cable emerging from thebackside can be laid at inconsistent depths in irregular terrain.

It will be appreciated from the foregoing that prior art devices presentproblems which are in need of solutions. The present invention providessolutions for these and other problems.

SUMMARY OF THE INVENTION

The present invention is directed to a linkage apparatus for connectinga use device, most preferably a vibrating cable laying plow apparatus,to a ground-engaging vehicle. The linkage apparatus includes: a firstarm member having first and second ends and a first mechanism forconnecting the first end to the vehicle; a second arm member havingfirst and second ends and a second mechanism for connecting the secondend to the use device; a third mechanism for pivotally connecting thefirst and second arm members; and a mechanism for dampening vibrationsbetween the first and second arm members. The dampening mechanismpreferably includes a resilient member which dampens vibrations,preferably an air cushion bag. More preferably, the dampening mechanismincludes a resilient member on each side of the third pivotal connectingmechanism. The third pivotal connecting mechanism preferably includes asubstantially horizontal axis about which the first and second armmembers pivot. More preferably, the linkage apparatus also includes anupper mechanism for linking the use device to the vehicle which islocated above the first and second arm members and has first and secondends. The linkage apparatus preferably includes a fourth mechanism forpivotally connecting the first end of the upper linking mechanism to thevehicle, and a fifth mechanism for pivotally connecting the second endof the upper linking mechanism to the use device. The first connectingmechanism and the second connecting mechanism are preferably mechanismsfor pivotally connecting. The upper linking mechanism, preferablycooperates with the first and second arm members to substantially form afour point linkage having four pivotal connection points in a roughlyquadralateral orientation, and a fifth pivotal connection linking thefirst and second arms.

Preferably, the invention includes a mechanism for lifting the first armmember wherein the pivotal connecting mechanisms of the first and secondends of the upper linking mechanism, the first end of the first armmember, and the second end of the second arm member, have substantiallyhorizontal axes such that when the first arm member is lifted, the firstarm member and the upper linking mechanism pivot substantiallyhorizontally about their first end pivotal connecting mechanisms. Theupper linking mechanism preferably includes an upper linkage member anda mechanism for adjusting the length of the upper linkage member, suchthat the angle of alignment of the use device may be adjusted byadjusting the length of the upper linkage member.

The present invention offers many advantages over the prior art, some ofwhich are discussed below. The arrangement of the first and second armmembers, the third pivotal connecting mechanism and the dampeningmechanism allow the use of larger vibrating units which will direct morevibration to the use device, while minimizing the vibrations transferredfrom the use device to the vehicle. During operation, the vibratingcable plow of the present invention directs most of the force, ortorque, created by the ground as it resists the plow-blade which isbeing pulled through the ground, to the second connecting mechanismbetween the lower linking mechanism and the plow-blade. This is becausethis mechanism is the closest pivot point with respect to the forcevector which resists movement of the lower end of the plow-blade throughthe ground. Because the bulk of the force resisting the tractive pullingforce of the vehicle is therefore directed to the second connectingmechanism, the bulk of the vibrations from the plow-blade are directedalong the lower linking mechanism, and particularly, along the secondarm member which is pivotally attached to the first arm member. Ratherthan transferring the vibrations to the vehicle, however, the bulk ofthe vibrations along the lower linking mechanism are directed to thedampening mechanism interposed between elements of the first and secondarm members.

The pivotal movement of the first and second arm members with respect toone another, cooperate with the pulling force exerted on the plow-blade,the pivotal connecting mechanisms which allow other pivotal movement,and the tooth of the plow-blade, to urge the lower end portion of theplow-blade, specifically the tooth of the plow-blade, to follow anelliptical path. The upper surface of the tooth, and particularly thespecific angle of the upper surface of the tooth with respect to a lineperpendicular to the front edge of the plow-blade, blade, is veryimportant in creating this pattern of elliptical movement. The elementsdescribed above cooperate to effectively utilize the tractive pullingforce of the vehicle and the vibratory energy directed along the lowerlinking mechanism to provide the elliptical motion of the tooth whichworks the ground, thereby making it easier to pull the plow-blade.

The cycle of elliptical motion starts with the first and second armmembers in a substantially parallel relationship such that the straightline length is maximized between the distal ends of the lower linkingmechanism, meaning the first end of the first arm member and the secondend of the second arm member where the first and second connectingmechanisms are respectively located. When the arm members pivot suchthat the distance between their distal ends is shortened, since theradius of the pivot about the third connecting mechanism is shorter thanthe radius of the pivot about the fourth connecting mechanism, the lowerend of the plow-blade is drawn closer to the vehicle. At the same timeas the lower end is drawn closer, the angle of the upper surface of thetooth meets the ground at such an angle that it acts to force theplow-blade initially downward. The movement of the lower end of theplow-blade is, therefore, initially downward and toward the vehicle. Asthe plow-blade pivots, and as the angle of the surface of the toothchanges with respect to the vector of the tractive pulling force beingexerted on the plow-blade, the lower end of the plow-blade and the toothgradually turn upward and the tooth passes through the bottom of itselliptical cycle, and comes to the top of the pattern. Throughout thatpattern of movement, the tooth works the ground. Once the angle of thesurface of the tooth no longer forces the plow-blade downward, thedistance between the distal ends of the two arm members begin tolengthen. As this distance lengthens, the angle of the plow-blade andthe angle of the surface of the tooth with respect to the vector of thepulling force being exerted on the plow-blade change, returning to theoriginal angles. When the angles return to the original angles, and whenthe length between the ends of the lower linking mechanism is maximized,the tooth pulls the blade downward again and the distance between thedistal ends of the two arm members shortens again, and the ellipticalcycle begins a second path downward and toward the vehicle. It is thiselliptical pattern of movement which works the soil and reduces therequirement for tractive pulling force. For this reason, the presentinvention requires much less tractive pulling power than the prior artdevices, and therefore, does not require tractors as large as thosegenerally used with the prior art devices. It is understood that otherpatterns of motion are possible with other configurations of theelements discussed herein.

A further advantage of the present invention is the mechanism foradjusting the length of the upper linking member which allows the angleof the plow-blade with respect to the ground to be adjusted when theplow-blade is traversing irregular terrain. The ability to manipulatethe angle of the plow-blade with respect to the ground allows theoperator to go over a ridge and through a ditch while at the same timemaintaining the plow-blade at a perpendicular angle to the ground. Thisallows the operator to prevent the rear part of the lower end of theplow-blade, where the cable guide means generally release the cable intothe ground, from angling toward the surface with respect to the positionof the front edge of the lower end of the plow-blade. This manipulationallows operators to lay all the cable, even that laid in irregularterrain, at a consistent depth.

The above described features and advantages along with various otheradvantages and features of novelty are pointed out with particularity inthe claims of the present application. However, for a betterunderstanding of the invention, its advantages, and objects attained byits use, reference should be made to the drawings which form a furtherpart hereof and to the accompanying descriptive matter in whichpreferred embodiments of the invention are described and illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational perspective view of the linkage apparatus ofthe present invention connecting a cable plow apparatus to aground-engaging vehicle and shown in its environment pulling the plowthrough the ground.

FIG. 2 is a side view of the linkage apparatus of the present inventionconnected to a cable plow apparatus, wherein the lower linking mechanismis shown in partial cross section;

FIG. 3 is a side view similar to FIG. 2 wherein the first arm has beenraised;

FIG. 4 is a top view of the linkage apparatus connected to a vibratingcable plow apparatus;

FIG. 5 is a top view similar to FIG. 4 wherein the linkage apparatus isswung to one side of the vehicle and the plow-blade is angled in theopposite direction with respect to the linkage apparatus;

FIG. 6 is a top view of the lower linking mechanism showing a pivotalconnection between the first and second arms and air cushion bags inphantom;

FIG. 7 is a side view of the linkage apparatus connected to a cable plowapparatus, wherein the length of the upper linking mechanism issubstantially the same as the length of the lower linking mechanism;

FIG. 8 is a side view similar to FIG. 7 wherein the distance between thefirst end of the first arm and the second end of the second arm isshortened;

FIG. 9 is a side view similar to FIG. 7 wherein the upper linkingmechanism is longer;

FIG. 10 is a side view similar to FIG. 7 wherein the length of the upperlinking mechanism is shorter;

FIG. 11 is a cross-sectional view through line 11--11 of FIG. 2;

FIG. 12 is a side view of the lower portion of the cable plow; and

FIG. 13 is a perspective view of the lower portion of the cable plowshowing the upper surface of the tooth and the edge of the plow-blade.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

Referring to the drawings, FIG. 1 shows a preferred embodiment of alinkageapparatus 100 for connecting a use device, preferably a vibratingcable plow apparatus 200 as shown, to a ground-engaging vehicle,preferably a tractor 10. The tractor 10 can carry a large spool 12 fromwhich a continuous cable 14 is dispensed. The cable 14 passes betweentwo cable guide posts 205, into a cable guide chute 210 having a cableentrance 212 and a cable outlet 214.

The use device of the present invention may be any apparatus whichcauses vibrations. It may be any ground working device including a plow,preferably a cable plow, and most preferably a vibrating cable plow forlaying cable in the ground or subsurface.

The ground-engaging vehicle of the present invention can be a tractor ofvirtually any size having any type of traction devices. Since thepreferred embodiment of the present invention is capable of dampeningvibrations from a very large vibrator, thereby allowing the cable plowto use a large vibrator, the tractor may be much smaller and providemuch less tractive pulling force than would otherwise be required forlaying cable in occasionally heavily packed ground. For this reason, thetractor may have wheels, preferably rubber wheels which might nototherwise provide the required tractive pulling power to pull a cableplow through heavily packed ground.

Embodiments of the present invention may lay many types of cable,flexible pipe, conduit, tubing, and the like. Electrical cable iscommonly laid by such a device. Recently, devices which can lay cablewithout jarring the cable have been needed to lay fiber-optic cablewhich has small fiberglassfilaments in the center of a heavily insulatedcable. Any violent shaking or pounding of the fiber-optic cable maydamage it such that it is less effective in carrying transmissions.Therefore, a device which minimizes any violent concussion of the cablewould be a desirable apparatus for usein connection with laying such acable.

Referring now to FIGS. 1 and 2, the linkage apparatus 100 in accordancewith principals of the present invention, has an upper linkage mechanism138 and a lower linkage mechanism 108 which are pivotally connected suchthat the linkage apparatus 100 has a fourpoint linkage. The upperlinkage mechanism 138 includes an upper linking member 140 whichincludes two parallel upper linking arm members 142 which are adjustablein length. Each upper linking arm member 142 includes a sleeve 143 and asliding arm 144 which slides inside of the sleeve 143 to allowadjustment in length ofthe upper arm members 142. The upper linkingmechanism 138 also includes a hydraulic cylinder 146. Referring also toFIG. 3, 4 and 5, the hydraulic cylinder 146 is located between the upperarm members 142 and is connectedthereto. The hydraulic cylinder 146includes a sleeve 148 and a piston 149 in a typical hydraulic cylinder,sleeve and piston arrangement. Hydraulic cable lines 145 are connectedto a hydraulic control mechanism 18 in the vehicle 10 which supplieshydraulic power to drive the cylinder 146 in a conventional fashionknown to those of skill in the art. The upper linkingarm member 142 andthe piston 149 are pivotally connected to an outer support member 170.At the opposite end the upper linking arm members 142 are pivotallyconnected to a vertical support member 156.

The lower linking mechanism 108 includes a first arm member 110 and asecond arm member 120 which are pivotally connected. The distal ends ofthe lower linking mechanism, away from the pivotal connection 125 whichjoins the arm members 100 and 120, are pivotally connected to a verticalsupport member 156 and an outer linking mechanism 170. The first andsecond arm members 110 and 120 are pivotally connected about a pivotalconnection 125, including bushings 126 in the first and second armmembers110 and 120, and a pin 128 forming a substantially horizontalaxis. Still referring to FIGS. 1-5, along with FIG. 6, the first armmember 110 includes two parallel support members 112 which are connectedby a first plate member 113 and a second plate member 114 which areconnected to the parallel support members 112. A first end 110a of thefirst arm member 110is pivotally connected to the vertical supportmember 156. A pin 111 forming a horizontal axis passes through the firstend 110a of the first arm member 110, thereby passing through both ofthe parallel support members 112.

The second end 120b of the second arm member 120 also has a pivotalconnection 123. The second end 120b of the second arm member 120 ispreferably bifurcated into two second arm end members 122 which arejoinedto a second arm body member 124 which is connected to the secondarm end members 122 to form a single integral second arm member 120. Thesecond arm body member 124 is a flat metal, preferably steel alloy, bodyplate 127 supported by a number of horizontal beams 129. The body plate127 is substantially horizontal and is supported by four horizontalbeams 129 which are connected to the bottom surface of the body plate127 and oriented perpendicularly to the plane of the body plate 127.Bushings 126 extend through a receiving portion 127a and receive the pin128 which forms an axis about which the second arm member 120 pivots inrelation to the first arm member 110. The pin 128 passes through thebushings 126 and the first arm member 110 to pivotally connect the firstand second arm members 110 and 120 about the pivotal connection 125.

Interposed between the first plate member 113 and the second platemember 114 of the first arm member 110 and the body plate 127 of thesecond arm body member 124 of the second arm member 120, are air cushionbags 130 and132. These air cushion bags 130 and 132 are attached,preferably using fasteners, preferably bolts, to the first and secondplate members, 113 and 114 respectively, of the first arm member 110 andto the body plate 127 of the second arm body member 124. Additional aircushion bags can be added, but are not necessary.

The mechanism for dampening vibrations between the first and second armmembers may include any mechanism for cushioning an impact. Resilientmembers of the present invention may include hydraulic cushioningmechanisms, gas cushioning mechanisms such as gas pack struts or shockabsorbers, resilient springs of various types, including metal coils andother metal spring devices generally known in the art, hard or softrubberor polymer cushions or pucks, or the air cushion bags of thepreferred embodiment. The air cushion bags are similar to air bags usedto cushion semi-truck trailers. These air bags are used in the place ofstruts or shock absorbers and accomplish the same task. Such air bagsare generally made of vulcanized rubber or other materials similar tothe materials usedto construct rubber road tires. The air cushion bagsmay have intertubes ormay be tubeless. Preferably, they hold air and theair may be increased or decreased using appropriate mechanism. Duringoperation, the air cushion bags 130 and 132 cushion, or absorb, thevibrations between the first and second arm members 110 and 120, therebydampening the vibrations and reducing the transfer of vibrations to thevehicle.

The first end 110a of the first arm member 110 is pivotally connected tovertical support member 156 which is pivotally connected to vehicleframe 107. The first end 140a of the upper linking mechanism 140 is alsopivotally connected to the vertical support member 156 which ispivotally connected to the vehicle frame 107. The pivotal connections105 and 109 between the vertical support member 156 and the frame 107have substantially vertical axes which allow the linkage apparatus 100to swinghorizontally left and right with respect to the vehicle. In thepreferred embodiment, this motion is driven by hydraulic cylinders 150and 152 located on either side of the linkage apparatus 100 andpivotally connected to the frame 107 and the vertical support member156.

The vertical support member 156 is pivotally connected to asubstantially upright hydraulic cylinder 158. The hydraulic cylinder 158has a typical hydraulic cylinder, piston and sleeve arrangement. Thepiston 160 is pivotally connected to the first arm member 110 at apivotal connection point 162. All of the hydraulic cylinders are linkedto a hydraulic control mechanism 18 in the vehicle 10, the uprightcylinder 158 being so linked by hydraulic cables 163 and 164.

When the first arm member 110 is lifted by the hydraulic cylinder 158,the first arm member 110 pivots with respect to the second arm member120 on the horizontal axis of the pivotal connection 125, as well aswith respectto the vertical support member 156. Referring also to FIG. 7and 8, if the pivotal connection 125 lies on a straight line between thepivotal connections 111 and 123 of the first end 110a of the first armmember 110 and the second end 120b of the second arm member 120 when thefirst arm member 110 is lifted by the hydraulic cylinder 158, then, whenthe first arm member 110 pivots with respect to the second arm member120 on the horizontal axis of the pivotal connection 125, the pivotalconnection 111 will be drawn closer to the pivotal connection 123. Inaddition, when the second arm member pivots on the horizontal axis ofthe pivotal connection 125, the lower end 220 of the plow-blade 215 willbe drawn closer to the vehicle 10. This is because the second arm member120 will pivot on a shorter radius than the upper linking member 140pivots, thereby drawing the lower end 220 of the plow-blade 215 closerto the vehicle 10.

The outer linking mechanism 169 includes an outer support member 170which is pivotally connected to the second arm member 120 at the pivotalconnection 123 located at the second end 120b of the second arm member120. The outer support member 170 is also pivotally connected to theupperlinking mechanism 140 at a pivotal connection 172 at the second end140b ofthe upper linking mechanism 140.

Referring also to FIG. 9 and 10, the linkage apparatus of the preferredembodiment of the present invention forms a four-point linkage whichexists as a parallelogram-type linkage when the upper linking mechanism138 has the same length as the lower linking mechanism 108. Since theupper linking mechanism 138 includes a mechanism for adjusting thelength of the upper linking member 142, and since the straight linelength of thelower linkage mechanism 108 may also be varied, thefour-point linkage of the present invention need not exist at all timesas a parallelogram-type linkage. The upper linking member 142 may beshortened or lengthened with respect to the lower linking mechanism 108thereby changing the angle of the plow-blade 215 with respect to thelinkage apparatus 160 and the vehicle 10. Such adjustments of the upperlinking mechanism 138, may be used to vary the angle of the plow-blade215 with respect to the ground, thereby obtaining a desired angle withrespect to the ground when the plow-blade 215 traverses throughirregular terrain.

The plow apparatus of the present invention includes a plow-bladehousing 200 having a mechanism for receiving an upper end 235 of theplow-blade 215, wherein the housing 200 is pivotally attached to theouter support member 170. The housing 200 includes a bolt 260, whichpasses through an opening in the plow-blade 215, and through openings intwo vertical plates261 which extend identically down and along bothsides of the upper portion235 of the plow-blade 215, such that the bolt260 will pass through the openings in the vertical plates 261 of thehousing 200 and the opening in the plow-blade 215 to connect to theplow-blade 215 to the housing 200. The receiving mechanism includes abox 240 receiving the upper end 235 of the plow-blade 215. The box 240is connected to vibration mechanism, preferably an eccentric hydraulicvibrator 250. The hydraulic vibrator 250is connected to a hydrauliccontrol mechanism 18 by hydraulic cables 251 and 252 and is controlledin a conventional fashion as known to those skilled in the art. Anyvibrating mechanism generally known in the art maybe used with the cablelaying plow apparatus of the present invention. Referring also to FIG.11, the box 240 includes rubber strips 270 and metal strips 271 and 273which are packed around the plow-blade 215 such that the movement of theupper end 235 of the plow-blade 215 is restrictedto movement within thebox 240.

Referring also to FIG. 12 and 13, the plow-blade 215 has a front edge217, two vertically extending side surfaces 216 and a tooth 225. Thetooth 225 extends downwardly and outwardly from the front edge 217, andoutwardly from the side surfaces 216 of the plow-blade 215. Preferably,the upper surface 227 of the tooth 215 is aligned at an angle of about37°-43° with respect to a line which is perpendicular to thefront edge217 of the plow-blade 215.

The plow-blade preferably has a single opening through which a pin,preferably the bolt 260 is inserted to hold the plow-blade in place withrespect to the housing 200. The bolt 260 passes through openings in twovertical plates 261 which extend identically down and along on bothsides 216 of the plow-blade 215. The plow-blade 215 is substantiallyprevented from pivoting on bolt 260 by the box 240 receiving the upperend 235 of the plow-blade 215. The upper end of the plow-blade 235 istapered or truncated to fit into a slot in the bottom of the box 240.The plow-blade 215 does not come into direct contact with any portion ofthe box 240. Theupper end 235 of the plow-blade 215 received by the box240 is packed in a series of rubber strips 270 which cooperate with twometal strips 271 and 273 which cooperate to prevent substantial movementof the upper end 235 of the plow-blade 215 in the box 240. The metalplates 271 and 273 do not come into contact with the box 240, butinstead, only with the rubber strips 270. In other embodiments, therubber strips 270 may be made of anyresilient material known in the art.It is possible to interpose resilient material or packings between theupper portion 235 of the plow-blade 215 and the metal strips 271 and273. The metal strips 271 and 273 prevent theplow-blade from damagingthe rubber strips 270. The box also has a plate 241 on one side whichmay be removed to access the rubber strips 270 and the metal strips 271and 273. The plate 241 is attached to the box with fasteners, preferablybolts, which fasten the plate to a lip 243 on the edge of the adjacentside of the box 240.

The front edge 217 of the plow-blade 215 widens as it angles back to twoparallel sides 216 on either side of the plow-blade 215. The sides ofthe plow-blade 216 have weldings 218 which form cross-hatchings toprotect theplow-blade from wear. On the lower end 220 of the plow-blade215, the tooth225 extends downwardly and outwardly from the plow-blade215 with respect to the front edge 217 of the plow-blade 215, andoutwardly from the sides 216 of the plow-blade 215. The tooth 225 has anupper surface 227. The plane of the upper surface 227 of the tooth 225lies at an angle of about 37°-43° with respect to a line which isperpendicular to thefront edge 217 of the plow-blade 215. This edge 217is a substantially straight line oriented vertically with respect to theplow-blade 215. The angle of the tooth is preferably about 38°-42°, morepreferably about 39°-41°. The preferred embodiment has a tooth angle ofabout 41°.

The angle of the upper surface 227 of the tooth 225 with respect to theperpendicular line to the front edge 217 of the plow-blade 215 criticaltominimize the amount of drag which is experienced when pulling theplow-blade through the soil. If the angle is too great, for instancemore than 43°, the plow-blade 215 will have much greater resistance andwill require much greater tractive pulling force. However, if the angleistoo little, the eliptical motion of the tooth 225 during operation ofthe vibrator 250 and the tractor 10 will be minimized.

The upper surface 227 of the tooth 225 is also very important to theeliptical movement of the plow-blade 215, wherein the tooth 225 pullsthe lower portion 220 of the plow-blade 215 downward as the lowerportion 220 of the plow-blade 215 moves toward the tractor when thesecond arm member 120 pivots about the pivotal connection 125 to shortenthe distance between the distal ends of the lower linking mechanism 108.110. The tooth225 prevents the plow-blade 215 from riding up because thetooth 225 must work the soil which meets the upper surface 227 of thetooth 225. It will be appreciated that other configurations with respectto the distance between the ends of the various linking mechanisms andmembers will vary the critical angle for optimum elliptical motion, andthat other motions, therefore, will also be possible.

In the preferred embodiment, a cable guide chute 210 is pivotallyattached to the rear edge 219 of the plow-blade 215. The rear edge 219is flat having a plane which is roughly at right angles to the planes ofthe two vertical sides 216 of the plow-blade 215. The guide chute 210has four pivotal connections 209 which pivotally connect the chute 210to the plow-blade 215. The pivotal connections 209 allow the chute 210to pivot with respect to the plow-blade 215 on a vertical axis. Thechute 210 has acable entrance 212 which receives the cable 14 and acable outlet 214 whichguides the cable 14 into an opening or a trench inthe ground created by the plow-blade 215.

The housing 200 is pivotally connecting to the outer linking mechanism169.This mechanism includes a hydraulic cylinder 280 having a typicalhydrauliccylinder, piston and sleeve arrangement to pivot the plow-blade215 with respect to the outer linking mechanism 169 and the linkageapparatus 100. The hydraulic cylinder 280 is pivotally connected to thehousing 200 and pivotally connected to the outer linking support member170. The hydrauliccylinder 280 is connected to the hydraulic controlmechanism 18 by hydraulic cables 281 and 282. FIG. 5 presents a top viewof a linkage apparatus 100 connected to a housing 200, wherein thelinkage apparatus 100 is swung to one side with respect to the vehicle10 and the plow-blade215 and the housing 200 are swung in the oppositedirection with respect tothe outer linking mechanism 169 and the linkageapparatus 100.

FIG. 7 shows the four-point linkage of the linkage apparatus 100. Theupperlinking mechanism 138 is substantially equal in length to the lowerlinkingmechanism 108, thereby allowing the four-point linkage to effecta parallelogram-type linkage. In FIG. 8, however, the first arm member110 has been lifted by the hydraulic cylinder 158 such that the secondarm member 120 has pivoted at the pivotal connection 125 with respect tothe first arm member 110, thereby bringing the pivotal connection 111 ofthe first end 110a of the first arm member 110 closer to the pivotalconnection 123 of the second end 120b of the second arm member 120, andthereby changing the configuration so that there is no longer aparallelogram-type linkage. The lifting of the first arm member 110 hasdrawn the lower portion 220 of the plow-blade 215 closer to the vehicle10.

In FIG. 9, the length of the upper linking mechanism 138 has beenadjusted such that the upper linking mechanism 138 is longer than thelower linkingmechanism 108. The lower end 220 of the plow-blade 215 isdrawn closer to the vehicle 10 as the upper linking mechanism 138 islengthened. In FIG. 10, the length of the upper linking mechanism 138has been adjusted so that the upper linking mechanism 138 is shorterthan the lower linking mechanism 110. As the upper linking mechanism 138is shortened, the lower end 220 of the plow-blade 215 is moved furtheraway from the vehicle 10. Because the sleeve 143 is longer than thedistance between the pivotal connections 125 and 123 of the second armmember 120, the radius of the pivot of the upper linking mechanism 138will always be longer than the radius of the pivot of the second armmember 120 about the pivotal connection 125 which links the first andsecond arm members 110 and 120.

The adjustable length upper linking member 140, allows the plow-blade215 to be maintained at a desireable angle with respect to the groundsuch that the cable outlet 214 is not angled backward and raised abovethe depth of a leading corner 229 of the plow-blade 215, as it wouldhave to be at times when attached to prior art devices which do not haveadjustable length upper linking members. The ability to manipulate theangle of the plow-blade 215 with respect to the ground surface allowsthe operator to go over a ridge and through a ditch, while at the sametime maintaining the plow at a perpendicular angle to the surface. Thisallows the operator to prevent the cable outlet 214 at the back of thelower end 220 of the plow-blade 215, from angling toward the surfacewith respect tothe position of the leading corner 229 of the lower end220 of the plow-blade 215. This enables the operator to lay cable inirregular terrain while maintaining a substantially consistent cabledepth. This is desireable since the cable may be damaged if it isexposed on the surface of the ground. The deeper the cable, the safer itis considered to be. This is especially true in ditches or gulleys whichmay be subject to erosion at later points in time, thereby increasingthe likelihood that the cable may be exposed on the surface of theground.

All of the hydraulic cylinders shown in the drawings of the preferredembodiment of the present invention are connected to a hydraulic controlmechanism 18 in the vehicle 10 by hydraulic cables, some of which arebundled together in a cable bundle 162, which connects to the controlmechanism 18. The hydraulic cylinders are controlled in conventionalfashion as known to those skilled in the art.

While certain representative embodiments of the present invention havebeendescribed herein, for purposes of illustration, it will be apparentto those skilled in the art that modifications therein may be madewithout departing from the spirit and scope of the present invention.

What is claimed is:
 1. Linkage apparatus for connecting a use device toa ground-engaging vehicle, the linkage apparatus comprising: a first armmember having first and second ends; first means for connecting thefirst end to the vehicle; a second arm member having first and secondends; second means for connecting the second end of the second arm tothe use device; third means for pivotally connecting the first andsecond arm members, upper means for linking the use device to thevehicle, said upper linking means being located above the first andsecond arm members and having first and second ends; and means fordampening vibrations between the first and second arm members, saiddampening means including a resilient member interposed between thefirst and second arm members.
 2. The linkage apparatus of claim 1wherein the dampening means includes a resilient member which dampensvibrations between the first and second arm members.
 3. The linkageapparatus of claim 2 wherein the resilient member is an air cushion bag.4. The linkage apparatus of claim 1 wherein said dampening meansincludes a resilient member located on each side of said third pivotalconnecting means.
 5. The linkage apparatus of claim I wherein the thirdpivotal connecting means includes a substantially horizontal axis aboutwhich the first and second arm members pivot.
 6. The linkage apparatusof claim I including fourth means for pivotally connecting the first endof said upper linking means to the vehicle and fifth means for pivotallyconnecting the second end of said upper linking means to the use device,said first connecting means having means for pivoting said first end ofsaid first arm member with respect to the vehicle, and said secondconnecting means having means for pivoting said second end of saidsecond member with respect to the use device, wherein a four pointlinkage mechanism having four pivotal connection linkage points in aroughly quadralateral orientation and a fifth pivotal connection linkingthe first and second arms is formed.
 7. The linkage apparatus of claim 6including means for lifting the first arm member.
 8. The linkageapparatus of claim 6 wherein the upper linking means includes an upperlinkage member and means for adjusting the length of said upper linkagemember such that the angle of alignment of the use device with respectto a vertical line perpendicular to the plane of the vehicle may beadjusted by adjusting the length of the upper linkage member.
 9. Thelinkage apparatus of claim 6 wherein said four point linkage mechanismincludes a longitudinal vertical plane, wherein said fifth connectingmeans includes first means for attaching said upper linking means to theuse device, and wherein said second connecting means includes secondmeans for attaching said second arm member to the use device, said firstand second attaching means including means for adjusting the angle ofthe use device with respect to the longitudinal vertical plane.
 10. Thelinkage apparatus of claim 6 wherein said fourth connecting meansincludes third means for attaching said upper linking means to thevehicle, and wherein said first connecting means includes fourth meansfor attaching said first arm member to the vehicle; said attaching meansincluding means for swinging the first arm member and the upper linkingmeans from side to side with respect the vehicle.
 11. A plow apparatus,comprising:(a) a ground-engaging vehicle; (b) means for creating acontinuous trench in a ground subsurface when pulled by the vehicle,said trench creating means including a plow-blade; (c) means forvibrating said plow-blade; (d) linkage means for coupling the trenchcreating means to the vehicle, said linkage means including:(i) asupport member; (ii) means for attaching said support member to thevehicle; (iii) upper means for linking to said support member, saidupper linking means having first and second ends, said first end beingpivotally attached to said support member; (iv) lower means for linkingto said sup port member, said lower linking means having first andsecond ends and means for varying straight line length between saidfirst and second ends, the first end of said lower linking means beingpivotally attached to said support member; and (v) outer means forlinking the second ends of the upper linking means and the lower linkingmeans to the trench creating means, the second ends of the upper linkingmeans and the lower linking means being pivotally connected to saidouter linking means; and (e) means for pivoting said upper and lowerlinking means with respect to said vehicle about a substantiallyhorizontal axis.
 12. The plow apparatus of claim 11 wherein said lowerlinking means includes first and second arm members, and means fordampening vibrations between the first and second arm members, whereinsaid varying means includes means for pivotally connecting the first andsecond arm members, and wherein the first and second arm members havefirst and second ends, the first end of the first arm member being thefirst end of the lower linking means and the second end of the secondarm member being the second end of the lower linking means.
 13. The plowapparatus of claim 11 including means for swinging said linkage meansfrom side to side with respect to the vehicle.
 14. The plow apparatus ofclaim 11 including means for adjusting the angle of the plow-blade withrespect to the linkage means.
 15. The plow apparatus of claim 12 whereinthe dampening means includes resilient members located on opposite sidesof said pivotal connecting means such that the resilient members areinterposed between portions of the first and second arm members.
 16. Theplow apparatus of claim 15, wherein the resilient members are aircushion bags.
 17. The plow apparatus of claim 12 wherein said trenchcreating means includes a plow-blade housing having means for receivingsaid upper end of said plow-blade, said housing being pivotally attachedto said outer linking means.
 18. The plow apparatus of claim 17 whereinsaid plow-blade has an opening, wherein said trench creating meansincludes a pin which passes through said opening in the plow-blade, andmeans for connecting said pin to said plow-blade housing, said receivingmeans includes a box receiving the upper end of the plow-blade, saidreceiving means also including rubber strips and metal plates, the boxcontaining said rubber strips and said metal plates packed around theplow-blade such that the movement of the upper end of the plow-blade isrestricted to movement within said box.
 19. The plow apparatus of claim12 wherein the upper linking means includes means for maintaining theplow-blade at a desired angular orientation with respect to the surfaceof the ground as the vehicle traverses irregular terrain.
 20. The plowapparatus of claim 19 wherein the maintaining means includes means foradjusting the length of said upper linking means such that the angle ofalignment of the plow-blade with respect to the upper linking means maybe adjusted.
 21. The plow apparatus of claim 11 wherein said plow-bladehas a front edge, two vertically extending side surfaces, and a tooth,the tooth extending downwardly and outwardly from the front edge andoutwardly from the side surfaces of the plow-blade.
 22. The plowapparatus for claim 21 wherein the tooth has an upper surface, the uppersurface being aligned with respect to the front edge of the plow-bladesuch that the angle of the upper surface with respect to a line which isperpendicular to the front edge of the plow-blade is between 37 degreesand 43 degrees.
 23. The plow apparatus of claim 12, wherein said supportmember extends above said upper linking means and provides support forsaid pivoting means, said pivoting means including a hydraulic cylinder,said hydraulic cylinder being pivotally connected to said support memberand to said first arm member of said lower linking means.
 24. Avibrating cable plow apparatus for attachment to a ground-engagingvehicle and cooperation with means for guiding a continuous cable,wherein the cable guiding means cooperates with the plow apparatus tolay a continuous cable in a subsurface opening, the plow apparatuscomprising:(a) means for creating a continuous trench in a groundsubsurface, said trench creating means including an upright plow-bladehaving upper and lower ends; (b) means for vibrating said plow-blade;and (c) linkage means for coupling the trench creating means to thevehicle, said linkage means including;(i) a support member attaching tothe vehicle; (ii) upper means for linking to said support member, saidupper linking means including first and second ends, said first endbeing pivotally attached to said support member, said upper linkingmeans including means for adjusting the length of said upper linkingmeans; (iii) lower means for linking to said support member, said lowerlinking means including first and second arm members, said first andsecond arm members having first and second ends, the first end of thefirst arm member being pivotally attached to said support member, andthe second end of the second arm member being pivotally attached to saidtrench creating means, said lower linking means further including meansfor pivotally connecting the first and second arm members and means fordampening vibrations between the first and second arm members, saiddampening means including resilient members located on opposite sides ofsaid pivotal connecting means and being interposed between elements ofsaid first and second arm members, said pivotal connecting means havinga substantially horizontal axis about which said first and second armspivot; and (iv) outer means for linking the second ends of the upperlinking means and the second arm member of the lower linking means tosaid trench creating means.
 25. The cable plow apparatus of claim 24wherein the first arm member includes at least two parallel firstsupport members and at least two plate members extending therebetween,said dampening means further including means for attaching saidresilient members to said plate members, said plates being integrallyconnected to said parallel support members; and wherein the second armmember includes at least two second support members and a second armbody member extending therebetween, said dampening means including meansfor attaching said resilient members to said body member, said bodymember being integrally connected to said second support members, saidresilient members being interposed between said second arm body memberand said plate members.
 26. The cable plow apparatus of claim 24including means for pivoting said linkage means about said first ends ofsaid upper linking means and said first arm; means for pivoting theplow-blade on a vertical axis with respect to the linkage means; andmeans for pivoting said linkage means on a vertical axis with respect tothe vehicle.